1. Field of the Invention
The present invention relates to a method for sterilization of bacteria, microorganisms and the like.
2. Description of the Related Art
According to conventional methods of sterilization, objects to be sterilized are coated with a disinfectant or irradiated with ultraviolet rays when such objects cannot be heated to a high temperature.
Various methods for sterilization using far-infrared rays have been proposed. For example, food that absorbs these rays can be sterilized by irradiation of the rays. However, such methods do no more than heat the substance itself, such as food in which the bacteria are present or adhering, to a high temperature to kill the bacteria.
Among conventional sterilization methods, methods of heating to a high temperature damage the object such as human skin, tools or the like, while it is inconvenient to use a disinfectant because of the difficulty in achieving complete sterilization, because of the generation of bacteria resistant to the disinfectant, and because of its own harmful effects and odor. Methods of using ultraviolet radiation have drawbacks in that portions which are not irradiated are not sterilized and continuous radiation deteriorates the object.
Kokai (Jpn. Unexamined Patent Publication) 4-364853 discloses a method for sterilization by heating after a liquid is adhered to objects to be sterilized. The sterilization is effected by high temperature heating and the absorption characteristics of far-infrared rays are not taken into consideration.
Kokai (Jpn. Unexamined Patent Publication) 7-308369 teaches a sterilization technology of radiating far-infrared rays to objects to be sterilized after applying water having high far-infrared ray absorption. However, a large scale structure is needed to practice the invention, because it is necessary to use a device made specially for applying to the objects water having high far-infrared ray absorption. In addition, it is difficult to place body portions other than the fingers into the device. Because a far-infrared heater of a conventional ceramic type is used as a far-infrared radiation source, much time is needed to raise and lower the temperature of the heater. Therefore, the heater should always be active, thus consuming considerable energy, and is accordingly impractical. Although an infrared ray lamp and a halogen heater of which on-off change is carried out easily are used, their sterilization efficiency is extremely poor, because their far-infrared radiation efficiency is markedly inferior to that of a far-infrared heater. In addition, directly applied water leads to breeding of bacteria because of insufficient removal of residual water.
The first object of the invention is, therefore, to provide a simplified sterilization method not using a harmful medium such as a disinfectant or ultraviolet rays, and to provide a method using a means for effectively radiating far-infrared rays, whereby a simplified sterilization process can be performed on all desired portions of objects which cannot be heated to a high temperature.
The second object of the present invention is to provide a method which enables sterilization without directly supplying water to the objects.
According to the invention, there is provided a first method of sterilization, comprising applying water having high absorption of far-infrared rays or a liquid mixture of the water and ethanol to objects to be sterilized, and radiating far-infrared rays by use of a small carbon lamp which is highly efficient in radiating the rays, whereby objects are effectively sterilized.
According to the invention there is provided a second method of sterilization, comprising the steps of supplying a wet air or a saturated vapor as a source of a very small quantity of moisture around an object, and then radiating far-infrared rays by use of a carbon lamp.
The wet air or saturated vapor can be generated by supplying a liquid gas or an air including the liquid gas.
As the heating source for the carbon lamp, a carbon material having high far-infrared ray radiation efficiency is used. The material is sealed preferably with an inert gas such as argon, in a container made of a heat resistant material such as quartz.
The above method of supplying a very small quantity of moisture can be applied not only to sterilization of fingers but also to sterilization in order to preserve cultural assets since excess moisture is not supplied to and around the objects. Since the very small amount of moisture supplied according to the method of the present invention evaporates during the sterilization process, the following process of removing the moisture is not needed, and in addition, breeding of bacteria caused by residual moisture can be prevented.
The carbon material having high far-infrared ray radiation efficiency is obtained by mixing an excipient composition, which has a high yield of carbon residue after being sintered, with one or more kinds of carbon powder such as carbon black, graphite and coke, a metallic compound such as a metallic carbide, a metallic borate, a metallic silicate, a metallic nitrate, a metallic oxide, etc., molding and sintering the mixture to provide the product with a desired resistance during the sintering and carbonizing process. The product obtained has an optional specific resistance and form. It has been confirmed that the problems mentioned above are effectively solved because it is possible to control heat generation by a predetermined current and potential and because the product has excellent in heat generating performance and efficiency, as well as far-infrared generating performance.
The preferred embodiments of the present invention are described hereinafter, but it is to be understood that the invention is not limited to the embodiments.